1. Field of the Invention
The present invention relates to a valve-operating device for an internal combustion engine equipped with two cylinder banks and a variable valve timing and working angle mechanism, and specifically to a valve-operating device for a two-bank engine with a variable valve timing and working angle mechanism being capable of changing both valve timing and working angle (lifted period or valve-lift characteristic) of intake and/or exhaust valves depending on engine operating conditions by way of non-uniform rotation of a cylindrical hollow camshaft, mounted on the periphery of a drive shaft, about the drive shaft.
2. Description of the Prior Art
In recent years, there have been proposed and developed various types of variable valve timing and working angle mechanism which variably adjusts both valve timing and working angle of intake and/or exhaust valves. One such variable valve timing and working angle mechanism or device has been disclosed in Japanese Utility Model Provisional Publication No. 57-198306 or Japanese Patent Provisional Publication No. 6-185321, each of which employs a principle of a non-uniform velocity joint. In the conventional variable valve timing and working angle devices as disclosed in the Japanese Utility Model Provisional Publication No. 57-198306 and Japanese Patent Provisional Publication No. 6-185321, a cylindrical camshaft is provided on the outer periphery of a drive shaft rotating in synchronization with rotation of the engine. The cylindrical camshaft is divided for every engine cylinders. One shaft end of the divided cylindrical camshaft has a flanged end portion. A flanged sleeve is fixedly connected to the drive shaft, while opposing to the flanged end of the divided camshaft. The flanged end of the divided camshaft has a radial groove, while the flanged end of the sleeve fixed to the drive shaft also has a radial groove, in such a manner that the angular phase of the radial groove formed in the flanged camshaft end is offset from the angular phase of the radial groove formed in the flanged sleeve by 180 degrees. An annular disc is interleaved between the two opposing flanged end faces of the flanged camshaft and the flanged sleeve and has a pair of diametrically-opposing axially-extending pins, each slidably engaging with the associated one of the radial grooves. A so-called control housing is also provided for rotatably receiving the previously-noted annular disc. The control housing is not stationary but displaceable in a direction perpendicular to the axis of the camshaft such that the displacement of the control housing produces eccentric motion of the annular disc relative to the central axis of the cylindrical camshaft (or the drive shaft). Changing the eccentricity of the annular disc to the camshaft varies a valve-lift characteristic. The Japanese Patent Provisional Publication No. 6-185321 also teaches the use of an eccentric cam rotatably fitted to the control housing, to produce the displacement of the control housing in the direction perpendicular to the axis of the camshaft. That is, the eccentric cam is integrally formed with a so-called control shaft parallel to the axis of the camshaft. The control housing is rockably or oscillatingly supported by a support shaft parallel to the axis of the camshaft. The control housing has an eccentric-cam hole into which the eccentric cam is rotatably fitted. The control shaft has a driven connection with an actuator such as a hydraulic actuator. As appreciated, the angular position of the control shaft is adjusted by means of the actuator, thus producing the displacement of the control housing in the direction perpendicular to the associated camshaft. When the previously-discussed conventional variable valve timing and working angle mechanism or device is applied to a V-type engine with two cylinder banks, the layout of the control housings and other component parts is basically symmetric about the engine centerline, since intake and exhaust valves arranged in a first bank of the left and right banks and intake and exhaust valves arranged in a second bank are generally symmetrical with respect to the engine centerline. In the conventional variable valve timing and working angle mechanism, when the central axis of the annular disc is eccentrically displaced from the central axis of the camshaft, the cylindrical camshaft slightly rotates relative to the drive shaft, thus slightly changing the angular phase of the camshaft relative to the drive shaft. This varies a valve timing. As is generally known, in V-type combustion engines, the drive shaft for the camshaft arranged in the left bank and the drive shaft for the camshaft arranged in the right bank rotate in the same rotational direction. Thus, in the conventional device shown in the Japanese Patent Provisional Publication No. 6-185321, when an eccentric motion of an annular disc arranged in the left bank and an eccentric motion of an annular disc arranged in the right bank are symmetrical with respect to the engine centerline due to the symmetrical layout, an angular phase of the camshaft arranged in one cylinder bank varies in a valve-timing advance direction with respect to the angular phase of the associated drive shaft, whereas an angular phase of the camshaft arranged in the other cylinder bank varies in a valve-timing retard direction with respect to the angular phase of the associated drive shaft. As a consequence, valve-lift characteristics of left and right banks slightly differ from each other.